Concave platforms of cooled industrial gas turbine (IGT) blades experience high metal temperature and thermal strain during operation. For example, the GE 7FA+e 1st stage turbine blade experiences severe thermo mechanical fatigue (TMF) initiated cracking at a leading edge and trailing edge of the platform that leads to high scrap rates and possible platform separation during operation. The crack results from a large, thin uncooled concave platform constrained by a relatively cooler airfoil and buttress structure that puts the platform in a state of high compressive strain at steady state operating conditions. The transient start-up condition results in a more severe compressive strain than steady state because of the large mass difference between the platform web and the rest of the component. Because of the mass difference the platform heats up more rapidly. Similarly the platform cools down more rapidly upon shutdown putting the platform into a tensile loading condition. The field parts also experience platform thermal barrier coating (TBC) spallation and significant platform oxidation.
Accordingly, it is an object of the present invention to provide a gas turbine blade assembly which overcomes the above-mentioned drawbacks and disadvantages.